The withdrawal and analysis of blood is a common procedure often performed, for example, within hospital facilities as a prelude to the administration of intravenous solutions. A conventional means utilized to accomplish such procedure comprises an evacuated tube constructed, for example, of glass and having a sterilized interior for receiving the blood sample. The open end of the tube is sealed by means of a rubber stopper, and the sealed tube is adapted to be disposed within a tube holder in order to accomplish the blood sampling procedure. A double-ended needle, having an axial bore defined therein, is threadedly secured to the tube holder, and in a conventional manner, the proximal end of the needle is employed to penetrate the individual's vein while the distal end of the needle will subsequently penetrate the evacuated tube stopper. As a result of the pressure differential defined between the evacuated tube and the blood vessel, blood flows from the individual's vein, through the needle, and into the sampling tube.
It is often necessary to take multiple blood samples from the individual in order to perform a battery of laboratory tests. As a matter of procedure, the double-ended needle is maintained within the person's vein while the evacuated tubes are simply interchanged in a successive manner by removing the filled tubes from the tube holder and replacing the same with empty tubes. As the insertion and removal of the distal end of the needle into and out of the sealing stopper is not always readily accomplished in a simple and easy manner, the individual may be subjected to a substantial amount of discomfort. In addition, tissue damage within the vein-puncture situs is also a likely deleterious side effect of the foregoing blood sampling procedure.
Subsequent to the blood sampling procedure, intravenous feeding of solutions or medications is often established as the requirements of the particular patient dictate. A catheter is conventionally employed for accomplishing intravenous feeding operations, and as this procedure is entirely separate from the blood sampling procedure, the catheter is normally inserted into a region of the patient wholly dissociated from the blood-sampling situs, or within the region of the sampling situs, as convenience may warrant. Nevertheless, the insertion of the catheter is accomplished by means of a needle cannula-catheter assembly which is separate and distinct from the blood-sampling needle. As a result, it is readily appreciated that at least two vein-puncture sites must be established in order to accomplish both the blood-sampling and intravenous-feeding procedures. Such techniques, of course, subject the individual to multiple periods of discomfort, and increase the likelihood of tissue damage.